Re: [2/5] C-SKY port: Backend implementation

[Sandra Loosemore <sandra@codesourcery.com>]

On 07/24/2018 03:24 PM, Jeff Law wrote:
>>
>>> Any thoughts on using the newer function descriptor bits rather than old
>>> style stack trampolines?
>>
>> Has that been committed?  I vaguely remembered discussion of a new way
>> to handle nested functions without using the trampoline interface, but I
>> couldn't find any documentation in the internals manual.
> It did.  See TARGET_CUSTOM_FUNCTION_DESCRIPTORS and the (relatively few)
> ports that define it.

Hmmm, I completely failed to make that connection from the docs -- the 
whole description of that hook is pretty gibberishy and I thought it was 
something for targets where the ABI already specifies some "standard 
calling sequence" using descriptors (C-SKY doesn't), rather than a 
generic alternative to executable trampolines.  Putting on my doc 
maintainer hat briefly, I can see this needs a lot of work.  :-(

Anyway, is this required for new ports nowadays?  If so, I at least know 
what to search for now.  At this point I couldn't say whether this would 
do anything to fix the situation on ck801 targets where there simply 
aren't enough spare registers available to the trampoline to both hold 
the static link and do an indirect jump.

-Sandra